This is a term that designates disorientation in time in which
a person feels that he has been to an unknown place before, or has previously
experienced a situation, or met a person before. Déjà vu is
an unexpected sensation of familiarity that applies to events, experiences,
sensory impressions, dreams, thoughts, statements, desires, emotions, dreams,
visits, the act of reading, the state of knowing, and, in general, the circumstances
of living. The term is French for "already seen," and was first
used to give a description to such experiences in 1876 by E. Letter Boirac,
who called it "le sensation du déjà vu." In 1896,
F. L. Arnaud introduced it to science. There is no adequate English equivalent
for the term "déjà vu."

The sensation of déjà vu has been found to be a common
psychological experience. According to a poll conducted in 1986 by the National
Opinion Research Council of the University of Chicago, 67 percent of Americans
reported instances of déjà vu, up from 58 percent in 1973.
In other studies the phenomenon has been reported experienced more among
women than men, and more among younger people than older people.

There is a wide variance in theories explaining déjà vu.
Some psychologists refer to it as "double cerebration." As early
as 1884, theories were advanced suggesting that one hemisphere of the brain
received information a split second earlier that the other half. In 1895,
the English psychical researcher Frederic W. H. Myers theorized that the
subconscious mind registered information sooner than the conscious mind.
The speculation of a biological process for déjà vu, if there
is any, has not been proven.

Those believing in reincarnation theorize that déjà vu
is caused by fragments of past-life memories being jarred to the surface
of the mind by familiar surroundings or people. Others theorize that the
phenomenon is caused by astral projection, or out-of-body experiences (OBEs),
where it is possible that individuals have visited places while in their
astral bodies during sleep. The sensation may be also connected to the fulfillment
of a condition as seen of felt in a premonition. Other possible explanations
are clairvoyance and telepathy.

Others say déjà vu is a product of the collective unconscious
as theorized by psychiatrist Carl G. Jung. They speculate that déjà
vu occurs when one draws on the collective memories of humankind. Jung himself
had an intense déjà vu experience during his first trip to
Africa. While looking out a train window he felt as if he was returning
to the land of his youth of five thousand years earlier. He described it
in Memories, Dreams, Reflections (60)
as "recognition of immemorially known."

However, many researchers are cautious when dealing with instances of
déjà vu because of the chance the person who experienced the
sensation may have read or seen something that is now in his unconsciousness
that triggers the impression. The most reliable subjects of are young children.
A.G.H.